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Biomedical subjects

W Long

Publications and source records attributed to W Long.

At least 55 records · Page 3Linked to original sources
PubMed1996

Temporal reasoning for diagnosis in a causal probabilistic knowledge base.

We have added temporal reasoning to the Heart Disease Program (HDP) to take advantage of the temporal constraints inherent in cardiovascular reasoning. Some processes take place over minutes while others take place over months or years and a strictly probabilistic formalism can generate hypotheses that are impossible given the temporal relationships involved. The HDP has temporal constraints on the causal relations specified in the knowledge base and temporal properties on the patient input provided by the user. These are used in two ways. First, they are used to constrain the generation of the pre-computed causal pathways through the model that speed the generation of hypotheses. Second, they are used to generate time intervals for the instantiated nodes in the hypotheses, which are matched and adjusted as nodes are added to each evolving hypothesis. This domain offers a number of challenges for temporal reasoning. Since the nature of diagnostic reasoning is inferring a causal explanation from the evidence, many of the temporal intervals have few constraints and the reasoning has to make maximum use of those that exist. Thus, the HDP uses a temporal interval representation that includes the earliest and latest beginning and ending specified by the constraints. Some of the disease states can be corrected but some of the manifestations may remain. For example, a valve disease such as aortic stenosis produces hypertrophy that remains long after the valve has been replaced. This requires multiple time intervals to account for the existing findings. This paper discusses the issues and solutions that have been developed for temporal reasoning integrated with a pseudo-Bayesian probabilistic network in this challenging domain for diagnosis.

Artificial Intelligence↗
PubMed1996

A placebo-controlled trial of prostacyclin in acute respiratory failure in COPD.

Although patients with COPD often have elevated pulmonary artery pressures (PAP) and pulmonary vascular resistance (PVR), it is uncertain whether treatment of this pulmonary hypertension is beneficial. We evaluated the extent of pulmonary hypertension in 16 patients with severe COPD complicated by acute respiratory failure and pulmonary hypertension. We assessed the hypothesis that the vasodilator prostacyclin (PGI2) would reduce PVR and improve systemic O2 transport. Patients with a COPD exacerbation requiring mechanical ventilation, and mean PAP greater than 30 mm Hg, were randomized to receive PGI2 or placebo, in addition to conventional therapy. Randomization to PGI2 or placebo therapy occurred 1 to 12 h after intubation, while the patient was mechanically ventilated. An optimal PGI2 dose (2 to 12 ng/kg/min, IV) was established in an initial dose-ranging study and then this dose was infused continuously for 48 h. PGI2 initially reduced PVR, but this effect dissipated within 24 h, indicating the development of tachyphylaxis. Tolerance to the adverse effects of PGI2 (tachycardia, hypotension, flushing, and headache) also developed over time. PGI2 treatment was associated with a significant fall in PaO2 but no increase in systemic oxygen transport. PGI2 proved to be a nonselective vasodilator that caused mild hypoxemia. Despite acute respiratory failure, pulmonary hypertension is mild in patients with severe COPD receiving mechanical ventilation and IV PGI2 is not beneficial in such patients.

Acute Disease↗
PubMed1995

Double-blind developmental evaluation at 1-year corrected age of 597 premature infants with birth weights from 500 to 1350 grams enrolled in three placebo-controlled trials of prophylactic synthetic surfactant. American Exosurf Neonatal Study Group I.

Infants enrolled in three clinical trials of prophylactic treatment for respiratory distress syndrome with a single dose of synthetic surfactant (Exosurf Neonatal) or air placebo were monitored through 1-year adjusted age. A total of 1046 infants with birth weights from 500 to 1350 gm were enrolled in the three trials; of the 735 infants who survived to 1 year of age, follow-up evaluations were completed for 597 (80%, air placebo group; 82%, synthetic surfactant group). Infants in the air placebo and synthetic surfactant treatment groups had no differences in general health, growth, or nerodevelopmental outcomes or impairments. These follow-up results at 1-year adjusted age for infants who received a single dose of synthetic surfactant indicate that a single dose of synthetic surfactant reduces mortality without increasing the absolute number or proportion of infants with impairments at 1 year of age.

Air↗
PubMed1995

One-year follow-up of 66 premature infants weighing 500 to 699 grams treated with a single dose of synthetic surfactant or air placebo at birth: results of a double-blind trial. American Exosurf Neonatal Study Group I.

In a multicenter, double-blind, placebo-controlled trial that enrolled 215 premature infants with birth weights of 500 to 699 gm, 106 infants were treated prophylactically with a single 5 ml/kg dose of synthetic surfactant and 109 infants were given an equivalent dose of air placebo shortly after birth. In each group, 40 children survived infancy: 36 children in the air placebo group and 30 children in the synthetic surfactant group were available for follow-up. Weight, height, and head circumference measurements were similar for both groups at 1-year adjusted age. Infants who received synthetic surfactant at birth had statistically similar Bayley Scales of Infant Development scores (mental developmental index, 92 vs 83; psychomotor developmental index, 87 vs 82) compared with controls. Mild to moderate impairments in the synthetic surfactant group were 7% versus 29% in the control group; these differences were not statistically significant. The incidence of retinopathy of prematurity, the number of hospital readmissions, the need for surgery after day 28, evidence of chronic lung disease, the need for respiratory support at 1-year adjusted age, and the incidence of allergies were also not different between the two groups. However, the proportion of infants surviving without impairment was modestly higher in the synthetic surfactant group (8%, air placebo group; 23%, synthetic surfactant group). The findings from this small study indicate that infants weighing 500 to 699 gm who receive a single prophylactic dose of synthetic surfactant at birth have neurodevelopmental outcomes at least equivalent to those of infants given air placebo at 1-year follow-up.

Air↗
PubMed1995

One-year follow-up of 273 infants with birth weights of 700 to 1100 grams after prophylactic treatment of respiratory distress syndrome with synthetic surfactant or air placebo. American Exosurf Neonatal Study Group I.

A single dose of synthetic surfactant was administered prophylactically to premature neonates with birth weights between 700 and 1100 gm. The effects of this treatment on neurodevelopmental, neurologic, and ophthalmologic outcomes, impairments, and general health status were examined during a follow-up evaluation at 1-year adjusted age. The study was a multicenter, parallel, randomized, double-blind comparison of 446 infants who received either air placebo (n = 222) or synthetic surfactant (n = 224). Follow-up evaluations were completed for 82% of surviving infants in both treatment groups. Neurodevelopmental outcome and growth were equivalent in the infants treated with synthetic surfactant and in the infants given air placebo. Impairments occurred in 38% of the infants treated with air placebo compared with 31% of those given synthetic surfactant; the difference was not statistically significant (relative risk 0.809, 95% confidence interval 0.585, 1.119). The incidence of asthma was significantly higher in the group of infants given air placebo (4% vs 10% for surfactant and air placebo, respectively, relative risk 0.391, 95% confidence intervals 0.157, 0.972). Other outcomes, including retinopathy of prematurity, hospital readmissions, surgery, and evidence of chronic lung disease, were not different. Administration of a single prophylactic dose of synthetic surfactant increases survival in infants with birth weights between 700 and 110 gm without increasing the number or proportion of impaired survivors.

Air↗
PubMed1995

Health and neurodevelopmental outcome at 1-year adjusted age in 508 infants weighing 700 to 1100 grams who received prophylaxis with one versus three doses of synthetic surfactant. American Exosurf Neonatal Study Groups I and II.

A three-dose prophylactic regimen of synthetic surfactant replacement has been shown to improve neonatal and 1-year survival rates in infants of 700 to 1100 gm birth weight when compared with a single prophylactic dose. The purpose of this study was to evaluate the growth, development, and late morbidity at 1 year adjusted age among the survivors of the 826 patients enrolled in the protocol. Complete follow-up data were obtained for 75% of the survivors in both groups. Chronic lung disease, need for respiratory support, neurologic disease requiring medication, visual or auditory impairments, and the incidence and severity of retinopathy of prematurity were equivalent in the two groups. The frequency of neurodevelopmental impairment was also comparable in the groups that received one dose versus three doses: moderate to severe cerebral palsy was found in 9% versus 6%, mental retardation assessed by Bayley Scales of Infant Development scores less than 69 was found in 16% vs 14%, and moderate to severe impairments of any kind were found in 33% vs 24%, respectively. Furthermore, the absolute number of impaired survivors was 92 in the three-dose group versus 106 in the one-dose group, despite a higher survival rate in the three-dose group. This study demonstrates that developmental outcomes of infants weighing 700 to 1100 gm who received three prophylactic doses of synthetic surfactant are at least as good as those of infants receiving a single dose, and that improving survival rates of very premature infants with synthetic surfactant does not result in increased numbers of infants with impairments.

Child Development↗
PubMed1995

Double-blind evaluation of developmental and health status to age 2 years of infants weighing 700 to 1350 grams treated prophylactically at birth with a single dose of synthetic surfactant or air placebo.

In a previously published article, we reported results of a two-center study of outcome to 28 days of 385 infants with birth weights from 700 to 1350 gm who were assigned randomly to receive a single 5 ml/kg intratracheal dose of either synthetic surfactant or air placebo. Infants treated with surfactant had a higher rate of survival to 28 days without bronchopulmonary dysplasia than did control subjects given an air placebo. The present study assessed survivors in early childhood to determine neurodevelopmental outcome and late morbidity. Two hundred fifty-eight surviving infants from both centers were evaluated at 1-year adjusted age; medical histories were obtained, standard physical and neurologic examinations were performed, and Bayley Scales of Infant Development were administered. Ophthalmologic examinations were performed at various times between 28 days and 1-year adjusted age. At 2-years adjusted age, 118 infants from one center were reevaluated with the same procedures and also had hearing and speech evaluations. Neither the 1-year assessment of the entire population nor the 2-year assessment of the one center's cohort revealed physical or neurodevelopmental differences between treatment groups. We conclude that administration of a single prophylactic dose of synthetic surfactant to premature infants with birth weights from 700 to 1350 grams results in improved survival rates to 28 days without bronchopulmonary dysplasia and is not associated with adverse health or neurodevelopmental effects at 1-year or 2-years adjusted age.

Air↗
PubMed1995

Double-blind 1-year follow-up of 1540 infants with respiratory distress syndrome randomized to rescue treatment with two doses of synthetic surfactant or air in four clinical trials. American and Canadian Exosurf Neonatal Study Groups.

Synthetic surfactant has been shown to reduce neonatal and 1-year mortality and neonatal morbidity in infants with respiratory distress syndrome. However, less is known about the effects of synthetic surfactant on developmental outcome and long-term morbidity. Four multicenter, randomized, placebo-controlled trials of synthetic surfactant administered as rescue therapy were conducted in the United States and Canada, with a total enrollment of 2224 patients. Double-blind developmental evaluations of survivors were conducted at 1 year of age (adjusted for prematurity) in all four trials. Of the 1802 patients enrolled in the placebo-controlled rescue trials who survived to 1 year, 1540 (85%) completed the 1-year follow-up evaluation. Height, weight, and head circumference measurements were not different in the treatment and control groups. Mean and median Bayley Scores of Infant Development for both the Mental Development Index and the Psychomotor Development Index were also equivalent. The incidence of impairments was not different in the two groups (mild to moderate impairment, 12% (92 of 745) for the air placebo group vs 11% (86 of 771) for the synthetic surfactant group; severe impairment, 15% (114 of 745) for the air placebo group vs 13% (102 of 771) for the synthetic surfactant group). No differences in rates of retinopathy of prematurity or hearing impairment were found in the treatment groups. The need for surgery after day 28 of life (relative risk, 0.779; 95% confidence interval, 0.665, 0.927) and the need for respiratory support at 1 year (relative risk, 0.525; 95% confidence intervals, 0.303, 0.911) were both reduced in the synthetic surfactant group. These results indicate that developmental outcome at 1 year of age is at least as good among infants with respiratory distress syndrome who received rescue therapy with synthetic surfactant as it is in infants who received air placebo; the results also indicate that the incidence of long-term morbidity is reduced.

Air↗
PubMed1995

One-year follow-up of 89 infants with birth weights of 500 to 749 grams and respiratory distress syndrome randomized to two rescue doses of synthetic surfactant or air placebo. Canadian Exosurf Neonatal Study Group. Canadian Exosurf Neonatal Follow-Up Group.

Double-blind neurodevelopmental and physical evaluations were conducted at 1-year adjusted age in 89 infants with birth weights of 500 to 749 gm who had respiratory distress syndrome in the neonatal period and were randomized to receive two rescue doses of a synthetic surfactant (Exosurf Neonatal, Burroughs Wellcome Co., Research Triangle Park, N.C.) or air placebo. The trial used a common protocol and was conducted at 13 hospitals; patients were entered in the trial between February 1988 and September 1990. Ninety-five percent of surviving infants were assessed. Growth and development in the two groups were equivalent. Mean Bayley Scales of Infant Development scores were comparable (mental development index, 79 +/- 22 vs 87 +/- 20; psychomotor development index, 73 +/- 18 vs 81 +/- 19 for air placebo and synthetic surfactant, respectively). The incidence of severe retinopathy of prematurity was significantly decreased in the surfactant group compared with the air placebo group (15% vs 34%; relative risk 0.428; 95% confidence interval 0.2 to 0.9). Overall, administration of surfactant appeared to increase the probability of a favorable outcome. Confirmation of the trends observed in this study would provide a strong rationale for the rescue use of synthetic surfactant in extremely low birth weight infants with respiratory distress syndrome even if overall mortality is not reduced.

Air↗
PubMed1995

One-year outcome in 232 premature infants with birth weights of 750 to 1249 grams and respiratory distress syndrome randomized to rescue treatment with two doses of synthetic surfactant or air placebo. Canadian Exosurf Neonatal Study Group.

A randomized, double-blind, placebo-controlled trial was performed in 13 hospitals in Canada to assess whether two rescue doses of a synthetic surfactant (Exosurf Neonatal) would reduce mortality and morbidity rates in neonates with respiratory distress syndrome who weighed from 750 to 1249 gm. As part of the original trial design, double-blind follow-up evaluations were performed at 1-year adjusted age. A total of 118 patients who received air placebo and 114 patients who received synthetic surfactant were evaluated at 1 year. Growth and development in the two groups were equivalent. Scores on the Bayley Scales of Infant Development were within the normal range for both groups (mental development index, 90 +/- 22 vs 92 +/- 22; psychomotor development index, 81 +/- 19 vs 87 +/- 22 for the air placebo and synthetic surfactant groups, respectively). However, in both groups the proportion of infants with any impairment (air placebo group, 43 of 118 (36%); synthetic surfactant group, 41 of 114 (36%) and severe impairment (air placebo group, 29 of 118 (25%); synthetic surfactant group, 21 of 114 (18%)) was substantial. We conclude that two rescue doses of synthetic surfactant in infants with RDS who weighed 750 to 1249 gm had no detrimental effect on developmental outcome or late morbidity. No long-term benefits to 12-months corrected age were observed with the use of surfactant in this weight class. Larger studies or meta-analyses of existing trials will be required to determine if there are any late outcome advantages associated with rescue use of synthetic surfactant in infants weighing 700 to 1249 gm.

Air↗
PubMed1995

One-year follow-up evaluation of 260 premature infants with respiratory distress syndrome and birth weights of 700 to 1350 grams randomized to two rescue doses of synthetic surfactant or air placebo. American Exosurf Neonatal Study Group I.

A multicenter, randomized, double-blind, placebo-controlled trial of synthetic surfactant therapy for premature infants with respiratory distress syndrome (RDS) and birth weights of 700 to 1350 gm demonstrated a reduction in severity of RDS, morbidity, and neonatal and 1-year mortality. Of the 419 infants who were entered in the study, 80% of the surviving infants in both the air placebo group (122) and the synthetic surfactant group (138) returned for the follow-up evaluation at 1-year adjusted age. The only significant difference observed at follow-up was a reduction in the incidence of mild cerebral palsy in the synthetic surfactant group (air placebo group, 8 of 122 (7%); synthetic surfactant group, 3 of 138 (2%); relative risk 0.306; 95% confidence interval 0.094, 0.999). No differences were observed between the air placebo and synthetic surfactant treatment groups with respect to health status of the infants, including the incidence of retinopathy of prematurity and neurodevelopmental delays. The difference in the overall incidence of impairment among the 1-year survivors in the air placebo group (43 of 122 (35%)) and in the synthetic surfactant group (40 of 138 (29%)) was not statistically significant. The results of this 1-year follow-up study show that rescue treatment with synthetic surfactant in infants weighing 700 to 1300 gm is not associated with adverse developmental consequences despite the improvement in survival.

Air↗
PubMed1995

Outcome at 1-year adjusted age of 957 infants weighing more than 1250 grams with respiratory distress syndrome randomized to receive synthetic surfactant or air placebo. American and Canadian Exosurf Neonatal Study Groups.

This study determined outcomes at 12-months adjusted age of 957 infants weighing more than 1250 gm at birth who were subjects in a randomized, double-blind, controlled trial of synthetic surfactant or air placebo administered in a rescue trial at 23 hospitals in the United States and 13 hospitals in Canada. Follow-up results were available for 475 of 563 surviving infants who received air placebo (84%) and 482 of 571 infants who received synthetic surfactant (84%). Developmental outcome was equivalent in the two groups. Morbidity was less in the synthetic surfactant group as assessed by the need for medication for chronic lung disease (52 of 475 (11%) for the air placebo group vs 32 of 482 (7%) for the synthetic surfactant group) or respiratory support (10 of 475 (2%) for the air placebo group vs 1 of 482 (< 1%) for the synthetic surfactant group) at 1-year adjusted age. Bayley Scales of Infant Development (mental development Index: 102 for both the air placebo and synthetic surfactant groups; psychomotor development index: 95 for the air placebo group vs 94 for the synthetic surfactant group) and impairment rates (94 of 475 (20%) for the air placebo group vs 86 of 482 (18%) for the synthetic surfactant group) were similar in the two groups. Infants weighing more than 1250 gm who have respiratory distress syndrome have previously been shown to have improved survival rates and lower neonatal morbidity after treatment with synthetic surfactant. These follow-up data confirm that developmental outcome as determined at 12-months adjusted age is at least as good in those receiving synthetic surfactant.

Air↗
PubMed1995

Double-blind, randomized, placebo-controlled Canadian multicenter trial of two doses of synthetic surfactant or air placebo in 224 infants weighing 500 to 749 grams with respiratory distress syndrome. Canadian Exosurf Neonatal Study Group.

In a multicenter, double-masked, placebo-controlled rescue trial conducted at 12 Canadian hospitals, two 5 ml/kg doses of a synthetic surfactant or air placebo were administered to 224 infants with birth weights of 500 to 749 gm who had established respiratory distress syndrome and an arterial/alveolar oxygen tension ratio of less than 0.22. The first dose was given between 2 and 24 hours of age; the second dose was given 12 hours later to the infants continuing to receive mechanical ventilation. Infants were stratified at study entry by birth weight and gender. Infants receiving synthetic surfactant showed significant improvements in alveolar-arterial oxygen tension gradient, arterial/alveolar oxygen tension ratio, and oxygen and ventilator requirements through day 7. In the group randomized to synthetic surfactant, significant improvements were seen in oxygen requirements at the first time point measured (2 hours; p = 0.02), in the alveolar-arterial oxygen tension gradient by the second time point measured (6 hours; p = 0.03), and in mean airway pressure after 6 hours. Overall mortality at 28 days was not significantly different in the two groups (50% vs 46%, air placebo group vs synthetic surfactant group; p = 0.586). Similarly, neither the incidence of bronchopulmonary dysplasia (37% vs 30%, air placebo group vs synthetic surfactant group; p = 0.089) nor the incidence of survival without BPD through 28 days (17% vs 26%, respectively; p = 0.070) was significantly different in the two groups. No significant differences in the incidence of safety-related outcomes or in adverse effects such as apnea or pulmonary hemorrhage were noted. These findings indicate that rescue therapy with synthetic surfactant results in physiologic improvements in very tiny premature infants, but improvements in overall mortality or other complications of respiratory distress syndrome were not documented in the sample evaluated.

Air↗
PubMed1995

Effects of two rescue doses of synthetic surfactant in 344 infants with respiratory distress syndrome weighing 750 to 1249 grams: a double-blind, placebo-controlled multicenter Canadian trial. Canadian Exosurf Neonatal Study Group.

In a multicenter, double-blind, placebo-controlled rescue trial conducted at 13 Canadian hospitals, two 5 ml/kg doses of a synthetic surfactant or air placebo were administered to 344 infants with birth weights of 750 to 1249 gm who had established respiratory distress syndrome and an arterial/alveolar oxygen tension ratio less than 0.22. The first dose was given between 2 and 24 hours of age, and the second dose was given 12 hours later to the infants remaining on mechanical ventilation. Infants were stratified at study entry by birth weight and gender. The trial was terminated short of the targeted sample size because significant reductions in mortality were observed in another rescue trial completed in the United States in the same weight class of infants. Despite premature termination of the trial, the rate of survival without bronchopulmonary dysplasia was increased (61% vs 52%; p = 0.046) in infants treated with surfactant. In addition, there was a significant reduction in the incidence of overall pulmonary air leak (46% vs 32%; p = 0.009), pneumothorax (27% vs 17%; p = 0.023), and pulmonary interstitial emphysema (40% vs 28%; p = 0.018) in infants treated with synthetic surfactant. There was no difference in the incidence of bronchopulmonary dysplasia, apnea, or pulmonary hemorrhage. Significant improvements in alveolar-arterial oxygen tension gradient, arterial/alveolar oxygen tension ratio, and oxygen and ventilator requirements through day 7 were present. These findings indicate that rescue therapy with synthetic surfactant can improve outcome for premature infants weighing 750 to 1249 gm with respiratory distress syndrome.

Air↗